I wasn't sure, so I looked up the definitions:
Trust: Firm reliance on the integrity, ability, or character of a person or thing.
That was pretty spot on or me.
It's the expectation of integrity, ability and character of another person. Two people can trust each other, even if their core beliefs differ, but only if they act with integrity towards each other. Values like lying, cheating and stealing are obviously not what people with integrity and character are all about, so it's obvious that when people do these, they become untrustworthy.
I know that trust is both objective, as a stand alone concept, and personal, like how tintin phrased it. Everyone understands and acknolwedges trust, but each look at it in a slightly different way. However the rules are always the same. Lie, cheat, steal and lose trust. Honour others and keep your promises and you gain trust.